Open flow production system and method for recovery of shallow oil reservoirs

ABSTRACT

Process and apparatus for recovering flowable oil from relatively shallow, porous oil-bearing formations which outcrop at or near the surface. One or more production systems are located in the outcrop area at the uppermost position of the structure, and oil flows by natural reservoir pressure, or fluid under pressure may be injected in the relatively lower regions of the formation for driving the oil upwardly to the production systems from which the oil is collected. The production systems are open at the bottom in the formation and communicate at their upper ends with the surface. The injection fluid can be supplied through wells formerly used for production purposes, or by new wells specifically provided for that purpose. Said production systems maximize flow capacity by providing an infinite well bore diameter in comparison with conventional producing wells.

States latent Thomas et a1.

211 App]. No.: 320,863

[52] US. Cl 166/268, 166/256, 166/265, 166/52 [51] Int. Cl E21b 43/00,E21b 43/20 [58] Field of Search 166/256, 265, 268, 272, 166/275, 305,314, 52, 67, 53

[5 6] References Cited UNITED STATES PATENTS 1,651,311 11/1927 Atkinson166/275 1,722,679 7/1929 Ranney 166/266 UX 2,173,556 9/1939 Hixon166/272 3,157,231 11/1964 Darley 166/268 3,215,198 l1/l965 Willman166/268 X OTHER PUBLICATIONS Uren, Petroleum Production Engineering,Exploita- Oct. 22, 1974 tion, Third Edition, McGraw-Hill Book Co. lnc.,N.Y., 1953, PP- 526-550.

Primary Examiner-Stephen J. Novosad Attorney, Agent, or Firm-Donald D.Jeffery 5 7] ABSTRACT Process and apparatus for recovering flowable oilfrom relatively shallow, porous oil-bearing formations which outcrop ator near the surface. One or more production systems are located in theoutcrop area at the uppermost position of the structure, and oil flowsby natural reservoir pressure, or fluid under pressure may be injectedin the relatively lower regions of the formation for driving the oilupwardly to the production systems from which the oil is collected. Theproduction systems are open at thebottom in the formation andcommunicate at their upper ends with the surface. The injection fluidcan be supplied through wells formerly used for production purposes, orby new wells specifically provided for that purpose. Said productionsystems maximize flow capacity by providing an infinite well ,borediameter in comparison with conventional producing wells.

9 Claims, 6 Drawing Figures PAIENTEU 001221974 I ma 2 or 2 E: Illa? :1 &d i

FIG.

FIG.4

l orEN Low ERonUcTroN SYSTEM AND METHOD FOR RECOVERY OF SHALLOW on.

RESERVOIRS BACKGROUND OF THE INVENTION The present invention relates asindicated to an open flow production system operating under nearatmospheric pressure for oil recovery from shallow oil reservoirs, andrelates more particularly to novel method and apparatus for recoveryingoil from reservoirs or formations which outcrop at or near the surface.

As well understood by those skilled in the art, the recovery of oil fromoil-bearing formations by normal production techniques is relativelyinefficient, that is, the amount of oil recovered'relative to the amountof oil present in the formation is relatively low, with such recovery inthe case of viscous heavy petroleum deposits being as low as 8-l5percent of the total amount of oil in place in the formation. This is ofcourse assuming the production of the oil is limited to primaryrecoverytechniques due to the normal gas or water drive naturally occurring inthe reservoir, with or without artificial lift means.

In order to improve the recovery, secondary or tertiary recoverytechniques of various forms and con cepts have been employed, all ofwhich are commonly characterized in a broad sense by the sweeping and repressurization of the formation so as to provide artificial drive to theoil for improved recovery through the production wells. In view of theeconomic aspects of the problem, secondary or tertiary recoverytechniques have reached fairly high levels of sophistication.

Although secondary and tertiary recovery techniques as presentlypracticed have greatly improved field recovery, there are certainrecognized disadvantages. Where the reservoirs are relatively shallow, acondition which the present invention is specifically directed to, therelatively low reservoir pressure requiresrelatively close well spacing,therefore requiring numerous production and injection wells whichrapidly raise field development costs. The additional wells must notonly be drilled but operated and maintained as well, and the cost ofdrilling, maintaining and operating the additional wells necessary tosuccessfully practice primary, secondary or tertiary recovery techniquesis oftentimes not economically justified by the increased oil recovery.

It has been recognized that where the oil-bearing formation outcrops ator near the surface, other techniques may be employed for recovering theoil from the reservoir. An article fully exploring the prospects ofmining the oil-containing bituminous rock deposits of shallow oil fieldsappears in the June, 1972 issue of Engineering and Mining Journal, pages132-138. Although technically feasible, the mining of shallow oil fieldsby open pit mining techniques inherently meets with certaindifficulties, not the least-of which is the safety and ecologicalconcern about the tailings produced in the maining operation.

It has also been recognized in the art, reference being made to US. Pat.No. 3,157,231, that oil can be recovered from relatively shallowformations by secondary recovery techniques with diluent or solvent, inwhich the oil is artificially driven from confined extraction areas to aconfined recovery area communicating with the surface and from which theaccumulated oil can be pumped. However, the process disclosed thereincom prises the pressurizing of the formation at or near the top thereofand the recovery of the oil at or near the down structure position ofthe formation, with the oil passing through relatively small outletholes into the recovery areafor removal therefrom in a confined areaisolated by installing sheet piling. The outlet holes are for thepurpose of passing the oil and extracting fluid but preventing thepassage of sand in any significant amounts. In this regard, it should benoted that patentee is concerned with the recovery of oil from tarsands, the handling of which presents difficulties well known to thosein the art. In the treatment disclosed, a diluent or solvent, such asnaphtha, is employed for extracting and carrying the oil through thereservoir. The injection of such an extracting agent into the upper partof the formation as disclosed increases the danger of uplifting theoverburden and is conducive to the creation of channeling, not tomention the failure to take advantage of the natural laws of hydraulics.In addition, the patented system does not utilize the natural boundariesof the reservoir, and the cost of installing artificial boundaries forconfining operating areas is prohibitive for economical fielddevelopment.

SUMMARY OF THE INVENTION With the above in mind, a principal object ofthe present invention is to provide method and apparatus for recoveringoil from shallow reservoirs by normal recovery techniques. In accordancewith the present invention, the oil in the reservoir can be driven tothe recovery area by natural flow, water flooding, fire flooding, orsimilar recovery techniques.

A further, more specific object of the present invention is to providean oil production system of the type described in which a relativelyshallow field is developed or redeveloped by forming and locating aproduction system excavated in the formation at or near the outcrop andto which the oil is driven for collection and removal. In accordancewith the invention, the production system is excavated and open at thebottom and maintained at essentially atmospheric pressure, and has alarge diameter and open area which is exposed to the formation therebyproviding in effect a large well bore thereby increasing fluid flow byvirtue of reducing the friction losses inherent in present recoverytechniques where the oil to be recovered is driven to relatively smallconventional well bores.

A still further object of the present invention is to provide an openflow production system particularly suited for shallow oil reservoirsand which is capable of recovering substantial quantities of oil in aneconomical manner, thereby permitting extraction of oil from lowproduction or abandoned fields and extending the useful lives thereof.

A still further object of the present invention is to provide an openflow production system with a maximum producing capacity by eliminatingproducing wells by virtue of the surface production systems, thereby notonly eliminating the otherwise high drilling costs but alsosignificantly reducing the operating and maintenance costs associatedwith the conventional producing wells.

These and other objects will become apparent as the followingdescription proceeds in specific reference to the application drawings.

BRIEF DESCRIPTION OF THE APPLICATION DRAWINGS FIG. 1 is a partiallysectioned perspective view through a shallow, oil-bearing formation,with one or more injection wells being illustrated in the relativelydown structure portions of the formation, and several oil productionsystems being shown where the formation outcrops at the surface;

FIG. 2 is a cross-sectional view through an oil production systememploying a standard cylindrical tank;

FIG. 3 is a vertical cross-sectional view through a modified oilproduction system;

FIG. 4 is a cross-sectional view taken on line 4-4 of FIG. 3;

FIG. 5 is a vertical cross-sectional view of a further modified form ofoil production system, and

FIG. 6 is a cross-sectional view taken on line 6-6 of FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to theapplication drawings, and initially to FIGS. 1 and 2, there isillustrated in FIG. 1 an oil bearing formation generally indicated at 10which outcrops at or near the surface S at 12, with the outcrop as shownextending substantially along the surface. As above explained, thepresent invention is particularly well suited for shallow, oil-bearingformations which outcrop at or near the surface, and it will beunderstood that the top of the formation could terminate slightly belowthe surface and the concepts of the invention nevertheless applied forrecovering the oil.

As shown, the formation 10 is bounded at its upper surface by animpermeable barrier and other strata which form the overburden 14 whichvaries in thickness due to the inclination of the formation 10, with thebottom of the formation 10 being defined by the impermeable formation16, which impermeable formations represent the boundaries of the oilbearing formation of the type typically found with oil-bearingreservoirs. The impermeability of both the upper and lower formations isof course of major importance for oil accumulations and implementingrecovery techniques which are employed so as to confine theinjectionfluids to the oilbearing formation.

With respect to the formation 10 itself, this is normally of a porousrock through which the mobile oil can pass as a result of reservoirpressure differential. The porous reservoir rock desired in accordancewith the present invention should not be confused with tar sands, theviscosity of which makes very difficult the driving of the tar oil alongthe formation unless the tar oil is previously extracted from the sandby a suitable reagent or solvent. In accordance with the presentinvention, the oil entrapped in the formation 10 can be driven from theformation to the production system through natural flow, waterinjection, thermal drive or other means.

It should further be noted that the formation 10 may represent either anew field or a shallow field of current low production capacity, or anabandoned field whose production has terminated. In either event, thesituation is typically one in which the further production of oil bypresent recovery techniques is not economically justified in view of thelow well productivity and the high field development costs, primarilydue to the development drilling and operation of injection and producingwells. Ideally, in accordance with the present invention, wells,generally indicated at 18, are present on the premises so as to minimizefield development costs. The wells 18, whose well bores are indicated at20, are at a down structure position and can be quickly converted fromproduction to injection wells when required so as to permit fluidinjection into the areas of the formation indicated at 22 and at 24. Ifthe wells 18 remain from a prior or current production operation, thewell bores can still be utilized as production or injection wellsthereby making more efficient the recovery process.

It should also be noted that if the oil-bearing formation 10 issufficiently extensive and the outcrop accessible, the drilling ofinjection wells of the type shown at 18 may be economically justified.In drilling, the well bores extend into the down structure portion ofthe formation 10, as shown in FIG. 1, whereby the liquid hydrocarbonsfollowing the injection process are driven upwardly through theformation by the driving fluid thereby taking advantages of theprinciples of hydraulics. When the injection fluid is injected at theupper part of the formation, there is greater change of breakthrough,channeling of the injection fluid at formation interface, and uplift ofthe. overburden.

A series of production systems commonly designated at 30 are positionedalong the outcrop 12 or near the surface, with a typical system beingshown in cross section in FIG. 2. As shown, the system is in the form ofa cylinder that can be constructed either of plate steel or concrete,and is open at the bottom and installed by excavating a hole to thedesired depth into the formation. The system can also be constructed byinstalling sheet piling as shown in FIG. 3 and excavating inside to thedesired depth. Alternatively, a cluster of pipes can be driven andexcavated or drilled into the formation with communicating perforationsif desired as shown in FIGS. 5 and 6. Excavating increases fluid flow byvirtue of producing the head on the reservoir fluids. Although notshown, the system 30 can be diametrically braced interiorly of thevessel so as to withstand the lateral forces resulting from theoverburden 32 and formation.

A head 34 is preferably provided over the system 30 for venting the gasthrough pipe 36, and to provide protection to the environment.

Disposed within the system 30 is a pipe 38 for withdrawing any watercollecting in the bottom portion of the system, with a pump 40 beingdisposed in the line. A similar pipe 42 and pump 44 are provided forwithdrawing the oil and/or emulsion collected in the system above theoil-water interface. Although not shown, it will be understood thatsuitable control equipment, such as oil and/or water level indicatorsmay be employed to effect automatic, periodic withdrawal of the oil andwater from the system. The oil can with little or no treatment betransported directly to a production storage area, and the water may betreated for reinjection.

As described, the cylinder which forms part of the system 30 illustratedin FIGS. 1 and 2 is open at the bottom, and if necessary or desirable alayer of packed gravel indicated generally at 46 can be provided at thebottom of the cylinder.

described have been given the same reference numeral with an attachedprime.

' Referring to the modification illustrated in FIGS.

3-4, the system 30" is comprised of a series of sheet pilings commonlydesignated at 60 the edges of which are flanged andmated as shown inFIG. 4. The abutting flanges can be connected to form a sealed jointbyany suitable meanssuch as mechanical interlocks, welding or the like.As shown in F104, the individual pilings are located or positioned so asto form a generally circular structure. The earth inside the pilings canbe excavated after the pilings are driven to the desired depth or, ifdesired, the pilings can be installed after excavation. v

The system illustrated in FIGS. 3-4 is otherwise similar to the FIGS.1-2 form of the invention as indicated by the primed reference numerals.v

Referring to the modification; shown in FIGS. 5-6, the production systemin this form comprises a cluster of pipes commonly designated at 70which are in abutting relationship as shown in FIG. 6. At their areas oftangency, the cylinders are intercommunicated at vertically spacedregions by means of perforations commonly designated at .7 2 formed inthe pipes 70. As shown in FIG. 5, theperforations 72 are generallylocated in the oil, water and upper regions of the pipes to permit levelbuild-up of the liquids-t0 facilitate removal of -the same from thesystem.

As shown in FIG. 5, each pipe is provided with a head 74 for closing thesame, and the liquids and vented gas are removed from the system in the"same manner as previously described.

Development of shallow oil reservoirs should be apparent from the abovedescription. The selection of a field for development is based onseveral factors such When the formation is selected, one or severalproduction systems are installed, with the number of such systemsdepending upon the extent of the outcrop and the potential recovery.Where production wells exist, they may be modified to permit theinjecting of fluids down the well bores 20 into the formation 10. Theformations selected will perferably contain flowable oil depositsrecoverable by primary, secondary or other tertiary recovery techniques.Injection takes place in the lower-regions of the structure, with theoil flowing in the path of least resistance upwardly toward the outcropand the production systems. The delay between initial injection andmigration of the oil into the production system will vary depending uponthe injection pressure and the length, porosity and permeability of theformation, viscosity of the oil, and the fluid previously produced. Themovement and producing capacity of the oil are of course greatlyinfluenced and expedited by the provision of a large excavation wellbore opening or openings such as provided by the production systems 30,as contrasted with thesubstantial frictionallosses occurring in typicalrecovery techniques where the oil is driven to relatively small boreconventional wells.

With respect to the production systems 30 and 30', these have been shownrather simplified in the application drawings, and it will be understoodthat the systems may include additional equipment such as heaters,separators, compressors, as the specific n atur'e and quantity of theoil produced may dictate.

As above indicated, the concept'of the present invention may also beemployed for new field development. Where geological explorationindicates the existence of a shallow, outcropping oilformation, thereservoir may be developed by providingone or more injection wells andproduction systems rather than numerous production wells to produce theoil from the reservoir in accordance with standard techniques. The fielddevelopment costs are thereby greatly reduced where the'geology permitsproduction of the oil in accordance with the invention concepts.

-We claim: v

1. A process of recovering flowable oil from a relatively shallow,porous oil-bearing formation which outcrops at or near the surface,comprising the steps of:

' a. locating, excavating and installing an oil production system at theuppermost portion of the formation at the outcrop or near the surfacethereof, said system communicating at its upperend with .the surface andbeing entire'ly open at its bottom end in said formation; I

b. injecting a fluid underpressure into the down structure position ofsaid formation in a region thereof spaced from said-production system,said fluid driving said oil upwardly through said formation to saidproduction system, the latter by virtue of its size operating atessentially atmospheric pressure, the reduction of hydrostatic head andsaid open bottom providing in effect a large, open well bore therebygreatly increasing production capacity and reducing friction lossesresulting from movement of the oil upwardly through theformation, and

c. removing the thus collected oil from said production system.

2. The process of claim 1 further including the injecting of fluid intoseveral locations in the down structure position of said formation insuitably spaced relation, and collecting the oil in a plurality ofspaced production systems.

3. The process of claiml further including separately collecting andremoving gas and oil produced from the production system and ventingfrom said production system gas produced with said oil, therebyestablishing predetermined pressure conditions in said system whichapproximates atmospheric pressure.

4. The process of claim l'wherein said pressurized fluid comprises waterin a liquid or vapor state.

5. Apparatus for recovering flowable oil from a relatively shallow,porous oil-bearing formation which outcrops at or near the surface,comprising:

a. means for injecting a fluid into the down structure position of saidformation so as todrive said oil ,toward said surface;

b. means in the form of at least one production system excavated andinstalled in the uppermost portion of the formation at the outcrop ornear the surface thereof, with said system communicating at its 7. Theapparatus of claim 5 wherein said production system comprises a tank.

8. The apparatus of claim 5 wherein said production system comprises aplurality of sheet pilings interconnected at their adjoining edges toprovide an enclosure for receiving the produced oil.

9. The apparatus of claim 5 wherein said production system comprises aplurality of cylindrical pipes arranged in a clustered, abuttingrelation, and means providing communication between adjoining pipes inthe regions of water, oil and gas collection.

1. A process of recovering flowable oil from a relatively shallow,porous oil-bearing formation which outcrops at or near the surface,comprising the steps of: a. locating, excavating and installing an oilproduction system at the uppermost portion of the formation at theoutcrop or near the surface thereof, said system communicating at itsupper end with the surface and being entirely open at its bottom end insaid formation; b. injecting a fluid underpressure into the downstructure position of said formation in a region thereof spaced fromsaid pRoduction system, said fluid driving said oil upwardly throughsaid formation to said production system, the latter by virtue of itssize operating at essentially atmospheric pressure, the reduction ofhydrostatic head and said open bottom providing in effect a large, openwell bore thereby greatly increasing production capacity and reducingfriction losses resulting from movement of the oil upwardly through theformation, and c. removing the thus collected oil from said productionsystem.
 2. The process of claim 1 further including the injecting offluid into several locations in the down structure position of saidformation in suitably spaced relation, and collecting the oil in aplurality of spaced production systems.
 3. The process of claim 1further including separately collecting and removing gas and oilproduced from the production system and venting from said productionsystem gas produced with said oil, thereby establishing predeterminedpressure conditions in said system which approximates atmosphericpressure.
 4. The process of claim 1 wherein said pressurized fluidcomprises water in a liquid or vapor state.
 5. Apparatus for recoveringflowable oil from a relatively shallow, porous oil-bearing formationwhich outcrops at or near the surface, comprising: a. means forinjecting a fluid into the down structure position of said formation soas to drive said oil toward said surface; b. means in the form of atleast one production system excavated and installed in the uppermostportion of the formation at the outcrop or near the surface thereof,with said system communicating at its upper end with the surface andoperated at essentially atmospheric pressure, and being entirely open atits bottom end in said formation, and c. means for removing from theproduction system the oil produced thereto from the reservoir underpressure.
 6. The apparatus of claim 5 wherein said injection meanscomprises a plurality of injection wells having well bores penetratingthe down structure portion of said formation in suitably spacedrelation, and further including a plurality of suitably spacedproduction systems.
 7. The apparatus of claim 5 wherein said productionsystem comprises a tank.
 8. The apparatus of claim 5 wherein saidproduction system comprises a plurality of sheet pilings interconnectedat their adjoining edges to provide an enclosure for receiving theproduced oil.
 9. The apparatus of claim 5 wherein said production systemcomprises a plurality of cylindrical pipes arranged in a clustered,abutting relation, and means providing communication between adjoiningpipes in the regions of water, oil and gas collection.